The invention discloses a degradable garbage bag and a preparation method thereof. The preparation raw materials of the garbage bag are all degradable materials, and the raw materials comprise a base material, an antioxidant and an enhancer, wherein the base material is prepared from the following raw materials in percentage by weight: 40 to 60 percent of synthetic fiber, 20 to 30 percent of natural fiber and 20 to 30 percent of stabilizer; the enhancer is prepared from the following raw materials in percentage by weight: 60 to 80 percent of agar and 20 to 40 percent of gelatin; the antioxidant is prepared from the following raw materials in percentage by weight: 40 to 60 percent of preservative, 18 to 30 percent of anti-radical agent and 18 to 30 percent of flexibilizer. The degradable garbage bag provided by the invention can be thoroughly degraded, and is high in intensity, good in toughness, simple in preparation method and suitable to be popularized.